Temperature compensated acoustic wave device with multilayer interdigital transducer electrode including buffer layer

ABSTRACT

A temperature compensated surface acoustic wave device is disclosed. The temperature compensated surface acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode over the piezoelectric layer, and a temperature compensation layer over the interdigital transducer electrode. The interdigital transducer electrode includes a first layer, a second layer over the first layer, and a buffer layer between the first layer and the second layer. A thermal conductivity of the second layer is greater than a thermal conductivity of the buffer layer. The buffer layer can be a titanium layer. A thickness of the buffer layer can be in a range of 20 nm to 200 nm, or in a range of 5% to 30% of a thickness of the interdigital transducer electrode.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57. Thisapplication claims the benefit of priority of U.S. ProvisionalApplication No. 63/315,873, filed Mar. 2, 2022, titled “ACOUSTIC WAVEDEVICE WITH IMPROVED RELIABILITY,” the disclosures of which is herebyincorporated by reference in its entirety and for all purposes.

BACKGROUND Field

Embodiments of the invention relate to acoustic wave devices, and inparticular, to temperature compensated surface acoustic wave devices.

Description of the Related Technology

Filters are used in radio frequency (RF) communication systems to allowsignals to pass through at discreet frequencies but reject any frequencyoutside of the specified range. An acoustic wave filter, which is usedwidely in the wireless communication field, can include a plurality ofresonators arranged to filter a radio frequency signal. Example acousticwave filters include surface acoustic wave (SAW) filters and bulkacoustic wave (BAW) filters. Acoustic wave filters can be implemented inradio frequency electronic systems. For instance, filters in a radiofrequency front end of a mobile phone can include acoustic wave filters.A plurality of acoustic wave filters can be arranged as a multiplexer.For example, two surface acoustic wave filters can be arranged as aduplexer.

Examples of RF communication systems with one or more filter modulesinclude, but are not limited to, mobile phones, tablets, base stations,network access points, customer-premises equipment (CPE), laptops, andwearable electronics. For example, in wireless devices that communicateusing a cellular standard, a wireless local area network (WLAN)standard, and/or any other suitable communication standard, a poweramplifier can be used for RF signal amplification. An RF signal can havea frequency in the range of about 30 kHz to 300 GHz, such as in therange of about 410 MHz to about 7.125 GHz for certain communicationsstandards.

SUMMARY

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

In one aspect, an acoustic wave device is disclosed. The acoustic wavedevice can include a substrate, an interdigital transducer electrodedisposed on the substrate, and a temperature compensation layer over theinterdigital transducer electrode. The interdigital transducer electrodeincludes a lower layer, an upper layer, and a buffer layer disposedbetween the lower layer and the upper layer. A modulus of elasticity ofthe buffer layer is less than a modulus of elasticity of the upperlayer. The buffer layer is configured to release stress between thelower layer and the upper layer caused due to a difference between acoefficient of thermal expansion of the lower layer and a coefficient ofthermal expansion of the upper layer.

In one embodiment, the modulus of elasticity of the buffer layer is lessthan a modulus of elasticity of the lower layer.

In one embodiment, the acoustic wave device further includes anintermetallic layer between the buffer layer and the upper layer.

In one embodiment, the buffer layer has a first temperature coefficientof expansion value less than a second temperature coefficient ofexpansion value of the upper layer.

In one embodiment, the buffer layer has a first temperature coefficientof expansion value larger than a third temperature coefficient ofexpansion value of the lower layer.

In one embodiment, the buffer layer includes titanium (Ti).

In one embodiment, the upper layer includes at least one of aluminium(Al), copper (Cu), silver (Ag), and gold (Au).

In one embodiment, the lower layer includes at least one of molybdenum(Mo), tungsten (W), and platinum (Pt).

In one embodiment, the thickness of the buffer layer is more than 20 nmand less than 1000 nm.

In one embodiment, a thickness of the upper layer is less than 500 nm,and a thickness of the lower layer is less than 500 nm.

In one embodiment, the interdigital transducer electrode furtherincludes an adhesion layer between the upper layer and the buffer layer.

In one aspect, a radio frequency module is disclosed. The radiofrequency module can include a packaging board that is configured toreceive a plurality of components, and an acoustic wave device mountedon the packaging board. The acoustic wave device includes a substrate,an interdigital transducer electrode disposed on the substrate, and atemperature compensation layer over the interdigital transducerelectrode. The interdigital transducer electrode includes a lower layer,an upper layer, and a buffer layer disposed between the lower layer andthe upper layer. A modulus of elasticity of the buffer layer being lessthan a modulus of elasticity of the upper layer. The buffer layer isconfigured to release stress between the lower layer and the upper layercaused due to a difference between a coefficient of thermal expansion ofthe lower layer and a coefficient of thermal expansion of the upperlayer.

In one embodiment, the buffer layer has a first temperature coefficientof expansion value that is less than a second temperature coefficient ofexpansion value of the upper layer.

In one embodiment, wherein the first temperature coefficient ofexpansion value of the buffer layer is larger than a third temperaturecoefficient of expansion value of the lower layer.

In one embodiment, the buffer layer includes titanium (Ti).

In one embodiment, the upper layer includes at least one of aluminium(Al), copper (Cu), silver (Ag), and gold (Au), and the lower layerincludes at least one of molybdenum (Mo), tungsten (W), and platinum(Pt).

In one embodiment, the thickness of the buffer layer is more than 20 nmand less than 1000 nm.

In one aspect, a mobile device comprising is disclosed. The mobiledevice can include an antenna that is configured to receive a radiofrequency signal, and a front end system that is configured tocommunicate with the antenna. The front end system includes an acousticwave device that includes a substrate, an interdigital transducerelectrode disposed on the substrate, and a temperature compensationlayer. The interdigital transducer electrode includes a lower layer, anupper layer, and a buffer layer disposed between the lower layer and theupper layer. A modulus of elasticity of the buffer layer is less than amodulus of elasticity of the upper layer. The buffer layer is configuredto release stress between the lower layer and the upper layer caused dueto a difference between a coefficient of thermal expansion of the lowerlayer and a coefficient of thermal expansion of the upper layer.

In one embodiment, the buffer layer has a first modulus of elasticityless than a third modulus of elasticity of the lower layer.

In one embodiment, the buffer layer has a first temperature coefficientof expansion value less than a second temperature coefficient ofexpansion value of the upper layer.

In one aspect, a temperature compensated surface acoustic wave device isdisclosed. The surface acoustic wave device can include a piezoelectriclayer, an interdigital transducer electrode over the piezoelectriclayer, and a temperature compensation layer over the interdigitaltransducer electrode. The interdigital transducer electrode including afirst layer, a second layer over the first layer, and a buffer layerbetween the first layer and the second layer. A thermal conductivity ofthe second layer is greater than a thermal conductivity of the bufferlayer. A thickness of the buffer layer being in a range of 20 nm to 200nm.

In one embodiment, the piezoelectric layer is a lithium niobate layerhaving a cut angle in a range of 116° to 134° and a thickness in a rangeof 100 μm and 350 μm.

In one embodiment, the thermal conductivity of the buffer layer isgreater than a thermal conductivity of the first layer.

In one embodiment, the interdigital transducer electrode has a taperedsidewall. A width of the first layer can be greater than a width of thesecond layer.

In one embodiment, a thickness of the buffer layer is in a range of 20nm to 100 nm.

In one embodiment, a thickness of the buffer layer is in a range of 5%to 30% of a thickness of the interdigital transducer electrode.

In one embodiment, a thickness of the buffer layer is a titanium layeror a chromium layer.

In one aspect, a temperature compensated surface acoustic wave device isdisclosed. The acoustic wave device can include a piezoelectric layer,an interdigital transducer electrode over the piezoelectric layer, and atemperature compensation layer over the interdigital transducerelectrode. The interdigital transducer electrode includes a first layer,a second layer over the first layer, and a titanium buffer layer betweenthe first layer and the second layer. A thickness of the titanium bufferlayer being in a range of 20 nm to 200 nm.

In one embodiment, the piezoelectric layer is a lithium niobate layerhaving a cut angle in a range of 116° to 134° and a thickness in a rangeof 100 μm and 350 μm.

In one embodiment, the first layer is a molybdenum layer, a tungstenlayer, or a platinum layer, and the second layer is an aluminum layer.

In one embodiment, the interdigital transducer electrode has a taperedsidewall, and a width of the first layer is greater than a width of thesecond layer.

In one embodiment, a thickness of the titanium buffer layer is in arange of 20 nm to 100 nm.

In one embodiment, a thickness of the titanium buffer layer is in arange of 5% to 30% of a thickness of the interdigital transducerelectrode.

In one aspect, a temperature compensated surface acoustic wave device isdisclosed. The acoustic wave device can include a piezoelectric layer,an interdigital transducer electrode over the piezoelectric layer, and atemperature compensation layer over the interdigital transducerelectrode. The interdigital transducer electrode includes a first layer,a second layer over the first layer, and a buffer layer between thefirst layer and the second layer. A thermal conductivity of the secondlayer is greater than a thermal conductivity of the buffer layer. Athickness of the buffer layer is in a range of 5% to 30% of a thicknessof the interdigital transducer electrode.

In one embodiment, the piezoelectric layer is a lithium niobate layerhaving a cut angle in a range of 116° to 134° and a thickness in a rangeof 100 μm and 350 μm.

In one embodiment, the first layer is a molybdenum layer, a tungstenlayer, or a platinum layer, and the second layer is an aluminum layer.

In one embodiment, the interdigital transducer electrode has a taperedsidewall, and a width of the first layer is greater than a width of thesecond layer.

In one embodiment, a thickness of the buffer layer is in a range of 20nm to 200 nm.

In one embodiment, a thickness of the buffer layer is a titanium layeror a chromium layer.

The present disclosure relates to U.S. patent application Ser. No.______ [Attorney Docket SKYWRKS.1310A1], titled “ACOUSTIC WAVE DEVICEWITH INTERDIGITAL TRANSDUCER ELECTRODE HAVING BUFFER LAYER,” filed oneven date herewith, the entire disclosure of which is herebyincorporated by reference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a mobile device.

FIG. 2A is a schematic diagram of a carrier aggregation system.

FIG. 2B is a schematic diagram of a carrier aggregation system.

FIG. 2C is a schematic diagram of a carrier aggregation system.

FIG. 2D is a schematic diagram of a carrier aggregation system.

FIG. 3A is a schematic block diagram of a module that includes a filter.

FIG. 3B is a schematic block diagram of a module that includes a filter.

FIG. 4 is a schematic cross-sectional side view of an acoustic wavedevice with an interdigital transducer (IDT) electrode including twodifferent materials.

FIG. 5 is a schematic cross-sectional side view of an acoustic wavedevice according to an embodiment of the present disclosure.

FIG. 6A shows a measured stress distribution in the acoustic wave deviceof FIG. 5 .

FIG. 6B shows a measured stress distribution in an acoustic wave deviceaccording to an embodiment.

FIGS. 7A-1 to 7C-2 show simulated stress distributions in differentacoustic wave devices.

FIGS. 8A-1 to 8C-2 are graphs showing simulated stress distributions indifferent acoustic wave devices

FIG. 9A is a graph showing the maximum stress in an acoustic wave deviceaccording to an embodiment simulated with different thicknesses of abuffer layer.

FIG. 9B is a schematic cross-sectional side view of an acoustic wavedevice according to an embodiment.

FIG. 10A is a schematic diagram of one embodiment of a packaged module.

FIG. 10B is a schematic cross-sectional side view of the packaged moduleof FIG. 10A.

FIG. 11 is a schematic diagram of one embodiment of a phone board.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

FIG. 1 is a schematic diagram of one example of a mobile device 100. Themobile device 100 includes a baseband system 101, a transceiver 102, afront end system 103, antennas 104, a power management system 105, amemory 106, a user interface 107, and a battery 108.

The mobile device 100 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G, WLAN (forinstance, Wi-Fi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 102 generates RF signals for transmission and processesincoming RF signals received from the antennas 104. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 1 as the transceiver 102. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 103 aids is conditioning signals transmitted toand/or received from the antennas 104. In the illustrated embodiment,the front end system 103 includes power amplifiers (PAs) 111, low noiseamplifiers (LNAs) 112, filters 113, switches 114, and duplexers 115.However, other implementations are possible.

For example, the front end system 103 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

In certain implementations, the mobile device 100 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band and/or in different bands.

The antennas 104 can include antennas used for a wide variety of typesof communications. For example, the antennas 104 can include antennasassociated transmitting and/or receiving signals associated with a widevariety of frequencies and communications standards.

In certain implementations, the antennas 104 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 100 can operate with beamforming in certainimplementations. For example, the front end system 103 can include phaseshifters having variable phase controlled by the transceiver 102.Additionally, the phase shifters are controlled to provide beamformation and directivity for transmission and/or reception of signalsusing the antennas 104. For example, in the context of signaltransmission, the phases of the transmit signals provided to theantennas 104 are controlled such that radiated signals from the antennas104 combine using constructive and destructive interference to generatean aggregate transmit signal exhibiting beam-like qualities with moresignal strength propagating in a given direction. In the context ofsignal reception, the phases are controlled such that more signal energyis received when the signal is arriving to the antennas 104 from aparticular direction. In certain implementations, the antennas 104include one or more arrays of antenna elements to enhance beamforming.

The baseband system 101 is coupled to the user interface 107 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 101 provides the transceiver 102with digital representations of transmit signals, which the transceiver102 processes to generate RF signals for transmission. The basebandsystem 101 also processes digital representations of received signalsprovided by the transceiver 102. As shown in FIG. 1 , the basebandsystem 101 is coupled to the memory 106 of facilitate operation of themobile device 100.

The memory 106 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 100 and/or to provide storage of user information.

The power management system 105 provides a number of power managementfunctions of the mobile device 100. The power management system 105 ofFIG. 1 includes an envelope tracker 160. As shown in FIG. 1 , the powermanagement system 105 receives a battery voltage form the battery 108.The battery 108 can be any suitable battery for use in the mobile device100, including, for example, a lithium-ion battery.

The mobile device 100 of FIG. 1 illustrates one example of an RFcommunication system that can include power amplifier(s) implemented inaccordance with one or more features of the present disclosure. However,the teachings herein are applicable to RF communication systemsimplemented in a wide variety of ways.

FIG. 2A is a schematic diagram of a carrier aggregation system 40. Theillustrated carrier aggregation system 40 includes power amplifiers 42Aand 42B, switches 43A and 43B, duplexers 44A and 44B, switches 45A and45B, diplexer 46, and antenna 47. The power amplifiers 42A and 42B caneach transmit an amplified RF signal associated with a differentcarrier. The switch 43A can be a band select switch. The switch 43A cancouple an output of the power amplifier 42A to a selected duplexer ofthe duplexers 44A. Each of the duplexers can include a transmit filterand receive filter. Any of the filters of the duplexers 44A and 44B canbe implemented in accordance with any suitable principles and advantagesdiscussed herein. The switch 45A can couple the selected duplexer of theduplexers 44A to the diplexer 46. The diplexer 46 can combine RF signalsprovided by the switches 45A and 45B into a carrier aggregation signalthat is transmitted by the antenna 47. The diplexer 46 can isolatedifferent frequency bands of a carrier aggregation signal received bythe antenna 47. The diplexers 46 is an example of a frequency domainmultiplexer. Other frequency domain multiplexers include a triplexer.Carrier aggregation systems that include triplexers can process carrieraggregation signals associated with three carriers. The switches 45A and45B and selected receive filters of the duplexers 44A and 44B canprovide RF signals with the isolated frequency bands to respectivereceive paths.

FIG. 2B is a schematic diagram of a carrier aggregation system 50. Theillustrated carrier aggregation system 50 includes power amplifiers 42Aand 42B, low noise amplifiers 52A and 52B, switches 53A and 53B, filters54A and 54B, diplexer 46, and antenna 47. The power amplifiers 42A and42B can each transmit an amplified RF signal associated with a differentcarrier. The switch 53A can be a transmit/receive switch. The switch 53Acan couple the filter 54A to an output of the power amplifier 42A in atransmit mode and to an input of the low noise amplifier 52A in areceive mode. The filter 54A and/or the filter 54B can be implemented inaccordance with any suitable principles and advantages discussed herein.The diplexer 46 can combine RF signals from the power amplifiers 42A and42B provided by the switches 53A and 53B into a carrier aggregationsignal that is transmitted by the antenna 47. The diplexer 46 canisolate different frequency bands of a carrier aggregation signalreceived by the antenna 47. The switches 53A and 53B and the filters 54Aand 54B can provide RF signals with the isolated frequency bands torespective low noise amplifiers 52A and 52B.

FIG. 2C is a schematic diagram of a carrier aggregation system 60 thatincludes multiplexers in signal paths between power amplifiers and anantenna. The illustrated carrier aggregation system 60 includes a lowband path, a medium band path, and a high band path. In certainapplications, a low band path can process radio frequency signals havinga frequency of less than 1 GHz, a medium band path can process radiofrequency signals having a frequency between 1 GHz and 2.2 GHz, and ahigh band path can process radio frequency signals having a frequencyabove 2.2 GHz.

A diplexer 46 can be included between RF signal paths and an antenna 47.The diplexer 46 can frequency multiplex radio frequency signals that arerelatively far away in frequency. The diplexer 46 can be implementedwith passive circuit elements having a relatively low loss. The diplexer46 can combine (for transmit) and separate (for receive) carriers ofcarrier aggregation signals.

As illustrated, the low band path includes a power amplifier 42Aconfigured to amplify a low band radio frequency signal, a band selectswitch 43A, and a multiplexer 64A. The band select switch 43A canelectrically connect the output of the power amplifier 42A to a selectedtransmit filter of the multiplexer 64A. The selected transmit filter canbe a band pass filter with pass band corresponding to a frequency of anoutput signal of the power amplifier 42A. The multiplexer 64A caninclude any suitable number of transmit filters and any suitable numberof receive filters. One or more of the transmit filters and/or one ormore of the receive filters can be implemented in accordance with anysuitable principles and advantages discussed herein. The multiplexer 64Acan have the same number of transmit filters as receive filters. In someinstances, the multiplexer 64A can have a different number of transmitfilters than receive filters.

As illustrated in FIG. 2C, the medium band path includes a poweramplifier 42B configured to amplify a medium band radio frequencysignal, a band select switch 43B, and a multiplexer 64B. The band selectswitch 43B can electrically connect the output of the power amplifier42B to a selected transmit filter of the multiplexer 64B. The selectedtransmit filter can be a band pass filter with pass band correspondingto a frequency of an output signal of the power amplifier 42B. Themultiplexer 64B can include any suitable number of transmit filters andany suitable number of receive filters. One or more of the transmitfilters and/or one or more of the receive filters can be implemented inaccordance with any suitable principles and advantages discussed herein.The multiplexer 64B can have the same number of transmit filters asreceive filters. In some instances, the multiplexer 64B can have adifferent number of transmit filters than receive filters.

In the illustrated carrier aggregation system 60, the high band pathincludes a power amplifier 42C configured to amplify a high band radiofrequency signal, a band select switch 43C, and a multiplexer 64C. Theband select switch 43C can electrically connect the output of the poweramplifier 42C to a selected transmit filter of the multiplexer 64C. Theselected transmit filter can be a band pass filter with pass bandcorresponding to a frequency of an output signal of the power amplifier42C. The multiplexer 64C can include any suitable number of transmitfilters and any suitable number of receive filters. One or more of thetransmit filters and/or one or more of the receive filters can beimplemented in accordance with any suitable principles and advantagesdiscussed herein. The multiplexer 64C can have the same number oftransmit filters as receive filters. In some instances, the multiplexer64C can have a different number of transmit filters than receivefilters.

A select switch 65 can selectively provide a radio frequency signal fromthe medium band path or the high band path to the diplexer 46.Accordingly, the carrier aggregation system 60 can process carrieraggregation signals with either a low band and high band combination ora low band and medium band combination.

FIG. 2D is a schematic diagram of a carrier aggregation system 70 thatincludes multiplexers in signal paths between power amplifiers and anantenna. The carrier aggregation system 70 is like the carrieraggregation system 60 of FIG. 2C, except that the carrier aggregationsystem 70 includes switch-plexing features. Switch-plexing can beimplemented in accordance with any suitable principles and advantagesdiscussed herein.

Switch-plexing can implement on-demand multiplexing. Some radiofrequency systems can operate in a single carrier mode for a majority oftime (e.g., about 95% of the time) and in a carrier aggregation mode fora minority of the time (e.g., about 5% of the time). Switch-plexing canreduce loading in a single carrier mode in which the radio frequencysystem can operate for the majority of the time relative to amultiplexer that includes filters having a fixed connection at a commonnode. Such a reduction in loading can be more significant when there area relatively larger number of filters included in multiplexer.

In the illustrated carrier aggregation system 70, duplexers 64B and 64Care selectively coupled to a diplexer 46 by way of a switch 75. Theswitch 75 is configured as a multi-close switch that can have two ormore throws active concurrently. Having multiple throws of the switch 75active concurrently can enable transmission and/or reception of carrieraggregation signals. The switch 75 can also have a single throw activeduring a single carrier mode. As illustrated, each duplexer of theduplexers 44A coupled to separate throws of the switch 75. Similarly,the illustrated duplexers 44B include a plurality of duplexers coupledto separate throws of the switch 75. Alternatively, instead of duplexersbeing coupled to each throw the switch 75 as illustrated in FIG. 2D, oneor more individual filters of a multiplexer can be coupled to adedicated throw of a switch coupled between the multiplexer and a commonnode. For instance, in some applications, such a switch could have twiceas many throws as the illustrated switch 75.

The filters discussed herein can be implemented in a variety of packagedmodules. Some example packaged modules will now be discussed in whichany suitable principles and advantages of the filters discussed hereincan be implemented. FIGS. 3A and 3B are schematic block diagrams ofillustrative packaged modules according to certain embodiments.

FIG. 3A is a schematic block diagram of a module 80 that includes apower amplifier 42, a switch 83, and filters 84 in accordance with oneor more embodiments. The module 80 can include a package that enclosesthe illustrated elements. The power amplifier 42, a switch 83, andfilters 84 can be disposed on a common packaging substrate. Thepackaging substrate can be a laminate substrate, for example. The switch83 can be a multi-throw radio frequency switch. The switch 83 canelectrically couple an output of the power amplifier 42 to a selectedfilter of the filters 84. The filters 84 can include any suitable numberof surface acoustic wave filters. One or more filters of the filters 84can be implemented in accordance with any suitable principles andadvantages disclosed herein.

FIG. 3B is a schematic block diagram of a module 85 that includes poweramplifiers 42A and 42B, switches 83A and 83B, and filters 84A and 84B inaccordance with one or more embodiments, and an antenna switch 88. Themodule 85 is like the module 80 of FIG. 18A, except the module 85includes an additional RF signal path and the antenna switch 88 arrangedto selectively couple a signal from the filters 84A or the filters 84Bto an antenna node. One or more filters of the filters 84A and/or 84Bcan be implemented in accordance with any suitable principles andadvantages disclosed herein. The additional RF signal path includes anadditional power amplifier 42B, and additional switch 83B, andadditional filters 84B. The different RF signal paths can be associatedwith different frequency bands and/or different modes of operation(e.g., different power modes, different signaling modes, etc.).

As discussed above, communications devices, such as mobile phones andthe like, use filters and sub-systems incorporating filters (such asduplexers, diplexers, and the like) to separate signals in differentfrequency bands, such as transmission and reception signals, forexample.

Temperature compensated surface acoustic wave (TCSAW) filter is widelyused for high performance RF module. Reliability of a TCSAW has a quiteimportant role for ensuring final module product reliability. Forexample, interdigital transducer (IDT) electrode has been regarded as akey of filter reliability. Meanwhile, the IDT electrode according toprior art may consist of two materials to achieve high conductivity andmass loading at the same time.

FIG. 4 is a schematic cross-sectional side view of an acoustic wavedevice 400 with an interdigital transducer (IDT) electrode 404 thatincludes two different materials. The acoustic wave device 400 includesa substrate 402, the IDT electrode 404, and a dielectric film 410. TheIDT electrode 404 includes a lower layer 406 and an upper layer 408. Inthis example, the substrate 402 can be a piezoelectric layer, such as alithium niobate (LiNbO₃) layer. The lower layer 406 is formed of atleast one of molybdenum (Mo), tungsten (W), and platinum (Pt). The upperlayer 408 is formed of at least one of aluminium (Al), copper (Cu),silver (Ag) and gold (Au). The dielectric film 510 is formed of silicondioxide (SiO₂). The dielectric film 510 can be a temperaturecompensation layer.

When two different metals are in contact with one another and havedifferent diffusivities, atoms from the faster diffusing metal readilydiffuse across the interface into the slower diffusing metal leavingvoids. These voids coalesce into what is known as Kirkendall porosity.These pores can serve as nucleation sites for cracks or causesignificant degradation to the mechanical or the electrical propertiesnear the interface. As diffusion is a temperature activated phenomenon,this process can be exacerbated by higher temperatures. Also, when amultilayer IDT electrode includes a layer (e.g., the lower layer 406)that has a relatively low thermal conductivity (e.g., a temperaturecoefficient of expansion (TCE) of 9 ppm or lower) and a layer (e.g., theupper layer 408) that has a relatively high thermal conductivity (e.g.,a temperature coefficient of expansion (TCE) of 15 ppm or greater), theTCE difference can apply excessive stress to the dielectric film 510 atan interface between the layers during operation of the acoustic wavedevice. The excessive stress can damage the acoustic wave device.Therefore, it is desired to develop an acoustic wave device withimproved reliability while taking advantages of using two differentmetals for IDT electrode, by reducing stress occurred on the IDTelectrode and even preventing the electromigration induced by thethermal stress. Hereinafter, acoustic wave devices with improvedreliability according is disclosed.

FIG. 5 is a schematic cross-sectional side view of an acoustic wavedevice 500 according to an embodiment of the present disclosure. Theacoustic wave device 500 according to an embodiment can be a SAW filter,or boundary wave filter with a shear horizontal (SH) mode. The acousticwave device 500 illustrated in FIG. 5 further includes a buffer layer520 added between the lower layer and upper layer of the IDT electrode.

The acoustic wave device 500 can include a substrate 502, at least oneelectrode 504, and a dielectric film 510. The substrate 502 can be apiezoelectric layer such as a lithium niobate (LiNbO₃) layer. In someembodiments, the substrate 502 can a LN layer having a cut angle in arange of 116° to 134° that enables the acoustic wave device 500 togenerate, for example, a Rayleigh mode surface acoustic wave. In someembodiments, the substrate 502 provides a medium in which an acousticwave can propagate. The substrate 502 can be sufficiently thick to avoidsignificant frequency variation. For example, a thickness of thesubstrate 502 can be in a range of 100 μm and 350 μm. The electrode 504is an interdigital transducer (IDT) electrode. The electrode 504 can bedisposed on the substrate to excite a boundary wave at the substrate502. The dielectric film 510 is formed to cover at least a part of thesubstrate 502 and the electrode 504. The dielectric film 510 can be asilicon dioxide (SiO₂). The dielectric film 510 can include a materialthat can bring a temperature coefficient of frequency closer to zero. Athickness of the dielectric film 510 may be between 500 nm and 4000 nm.

The electrode 504 can include a lower layer 506, an upper layer 508, anda buffer layer 520 between the lower layer 506 and the upper layer 508.Each layer of the electrode 504 can be configured in plate-shape havinga thickness. Each layer of the electrode 504 has respective modulus ofelasticity. The modulus elasticity is used for measuring a tensile orcompressive stiffness when a force is applied. The modulus elasticityquantifies the relationship between tensile/compressive stress (forceper unit area) and axial strain (proportional deformation) in the linearelastic region of a material. The modulus elasticity can be referred toas Young's modulus, or Young modulus (GPs: Giga-pascals). In addition,each layer of the electrode 504 has a respective temperature coefficientof expansion (TCE) value corresponding to the material used for eachlayer.

The lower layer 506 can be disposed on the substrate 502. The lowerlayer 506 can be in contact with the substrate 502. The lower layer 506can include a material that provides mass loading. That is, the lowerlayer 506 can have a mass density that is greater than the upper layer508 and/or high resistance. The lower layer 506 contributes to alinearity of the response of the acoustic wave device 500. According tosome embodiments, the lower layer 506 can include one of molybdenum(Mo), tungsten (W), and platinum (Pt). The lower layer 506 can have athickness less than 500 nm. In some embodiments, the thickness of thelower layer 506 can be in a range from 0.03L to 0.10L (e.g., about0.08L). For example, when the wavelength L is about 4 μm, the thicknessof the lower layer 506 can be about 320 nm.

The upper layer 508 can be disposed at an upper portion of the electrode504. The upper layer 508 can include a material that provides highconductivity. The upper layer 508 can be formed of at least one ofaluminium (Al), copper (Cu), silver (Ag) and gold (Au). The upper layer508 can have a thickness less than 500 nm. In some embodiments, thethickness t3 of the upper layer 508 can be in a range from 0.02L to0.08L (e.g., about 0.04L). For example, when the wavelength L is about 4μm, the thickness of the upper layer 508 can be about 160 nm. In someembodiments, the electrode 504 may include alloys, such as AlMgCu, AlCu,etc.

The buffer layer 520 can be disposed between the lower layer 506 and theupper layer 508 to enhance the reliability of the acoustic wave device500. More specifically, the buffer layer 520 disposed between the lowerlayer 506 and the upper layer 508 can function as a transition layer torelax stress due to different moduli of elasticity in the lower layer506 and the upper layer 508. The buffer layer 520 may be referred to asa release layer. Since the lower layer 506 and the upper layer 508 havedifferent characteristics in response to a stress that is applied to theelectrode 504, the boundaries of the lower layer 506 and the upper layer508 are vulnerable to the external stress. According to someembodiments, the buffer layer 520 has a first modulus of elasticitylarger than a second modulus of elasticity of the upper layer 508.According to some embodiments, the buffer layer 520 has the firstmodulus of elasticity less than a third modulus of elasticity of thelower layer 506. In some embodiments, the buffer layer 520 can includetitanium (Ti), chromium (Cr), or a like material. Any suitablecombinations of the materials of the lower layer 506, the upper layer508, and the buffer layer 520 disclosed herein can be beneficial.

According to some embodiments, the lower layer 506 can include Mo whosethird modulus of elasticity is 327 [GPs], the upper layer 508 caninclude Al whose second modulus of elasticity is 70 [GPs], and thebuffer layer 520 can include Ti whose first modulus of elasticity is 108[GPs].

According to an embodiment, the lower layer 506 can include W whosethird modulus of elasticity is 345 [GPs], the upper layer 508 caninclude Al whose second modulus of elasticity is 70 [GPs], and thebuffer layer 520 can include Ti whose first modulus of elasticity is 108[GPs].

According to an embodiment, the lower layer 506 can include Pt whosethird modulus of elasticity is 168 [GPs], the upper layer 508 caninclude Al whose second modulus of elasticity is 70 [GPs], and thebuffer layer 520 can include whose first modulus of elasticity is 108[GPs].

In addition, the buffer layer 520 is configured to relax thermalexpansion stress. The thermal expansion stress is caused by differentialof temperature coefficient of expansion (TCE) between the lower layer506 and the upper layer 508. The buffer layer 520 has a firsttemperature coefficient of expansion (TCE) value less than a second TCEvalue of the upper layer 508. Additionally, the buffer layer 520 mayhave a first TCE larger than a third TCE value of the lower layer 506.For example, the first TCE value of the buffer layer 520 is less thanthe second TCE value of the upper layer 508, and larger than the thirdTCE value of the lower layer 506.

According to some embodiments, the lower layer 506 can include Mo whoseTCE value is 4.8 ppm (part per million), the upper layer 508 can includeAl whose TCE value is 23 ppm, and the buffer layer 520 can include Tiwhose TCE value is 8.6 ppm.

According to some embodiments, the lower layer 506 is formed of W whoseTCE value is 4.5 ppm, the upper layer 508 is formed of Al whose TCEvalue is 23 ppm, and the buffer layer 520 is formed of Ti whose TCEvalue is 8.6 ppm.

In some embodiments, the substrate 502 can include LN whose TCE value is15.7 ppm, and the dielectric film 510 can include SiO₂ whose TCE valueis 4.5 ppm.

The technical effect of reducing stress depends at least in part on athickness of the buffer layer 520. When the thickness of the bufferlayer 520 is too thin, the buffer layer 520 may not sufficiently work asthe transition layer between the lower layer 506 and the upper layer508. According to an embodiment, the thickness of the buffer layer 520can be 20 nm or greater. On the other hand, when the buffer layer 520 istoo thick, the advantage of combining the lower layer 506 and the upperlayer 508 is reduced due to the distance between the lower layer 506 andthe upper layer 508. Also, from a design perspective, excessivethickness of the buffer layer 520 may not be preferred as it canincrease the overall thickness of the acoustic wave device 500.According to some embodiments, the thickness of the buffer layer 520 canbe less than 1000 nm. For example, the buffer layer 520 can have athickness in a range of 20 nm to 1000 nm, 20 nm to 200 nm, 20 nm to 100nm, 30 nm to 200 nm, or 50 nm to 100 nm. In some embodiments, thethickness of the buffer layer 520 can be in a range of 5% to 30%, 10% to30%, or 5% to 20% of the total thickness of the electrode 504.

According to some embodiments, at least a portion of the buffer layer520 and at least a portion of the upper layer 508 can form anintermetallic layer at an interface between the buffer layer 520 and theupper layer 508. In some embodiments, the intermetallic layer mayinclude titanium aluminide (TiAl₃), formed at elevated temperatures bythe solid state reaction between metallic aluminum and metallictitanium, when, for example, the upper layer 508 is formed of Al and thebuffer layer 520 is formed of Ti. The intermetallic layer provides highconductivity, and therefore it enables to increase resistivity of theelectrode 504 as compared to other materials with lower conductivities.In addition, the intermetallic layer can prevent or mitigate migrationof atoms from the upper layer 508 into the buffer layer 520. Morespecifically, the intermetallic layer generates an electricallyconductive diffusion barrier that prevents or mitigates the migrationbetween two metal layers. Therefore, the buffer layer 520 can besufficiently hard so as to prevent or mitigate stress-inducedelectromigration. Thus the buffer layer 520 can enable the acoustic wavedevice 500 to me more reliable as the stress-induced electromigrationcan cause cracks when certain degrees of heat is applied.

In addition, by adding buffer layer 520 between the lower layer 506 andthe upper layer 508, improved crystallinity of the upper layer 508 wouldresult from the suppression of interfacial diffusion. The prevention ormitigation of a more disordered structure would decrease the resistivityof layer 508, thus improving performance. Thus, resistivity and electromigration durability of the acoustic wave device 500 can be improved.

According to some embodiments, the electrode 504 further includes anadhesion layer (not shown) below the upper layer 508. For example, theadhesion layer can include tantalum (Ta). A thin adhesion layer may beconfigured to provide high surface energy so as to enable more atoms tomove to order lattice. By adding the adhesion layer, the crystallinitycan be improved, and therefore the adhesion of the upper layer 508 canbe further improved.

FIG. 6A shows a measured stress distribution in the acoustic wave device400 that includes a molybdenum (Mo) IDT layer. The result of measuredthermal stress in the acoustic wave device 400 is represented indifferent types of shades. In the measurement, the acoustic wave device400 includes a substrate 402 formed of LN, an IDT electrode 404, and adielectric film 410 formed of SiO₂. The IDT electrode 404 includes alower layer 406 formed of Mo, and an upper layer 408 formed of Al.

The stress in the acoustic wave device 400 is mainly generated at ornear the surface of the IDT electrode 404, in particular at or near theedges of the lower layer 406. FIG. 6A indicates a relatively high stressat or near the edges of the lower layer 406 (indicated as an area (a)),which leads to degraded reliability. The area (a) of FIG. 6A indicatesthat the stress can be generated more at the edge of the lower layer 406closer to the upper layer 408.

FIG. 6B shows a measured stress distribution in the acoustic wave device500 according to an embodiment that includes a molybdenum (Mo) IDTlayer. In the measurement of FIG. 6B, a lithium niobate (LN) layer isused as the substrate 502, a molybdenum (Mo) layer is used as the lowerlayer 506, an aluminum (Al) layer is used as the upper layer 508, atitanium (Ti) layer is used as the buffer layer 520, and a silicondioxide (SiO₂) layer is used as the dielectric film 510.

FIG. 6B indicates that the stress in the acoustic wave device 500 isreduced as compared to the acoustic wave device 400 of FIG. 6A. An area(b) of FIG. 6B, indicates that the edge of the lower layer 506 has lessstress as compared to the edge of the lower layer 406 shown in FIG. 6A.In FIG. 6B, since the stress is reduced relative to the result of FIG.6A, the reliability of the acoustic wave device 500 is enhanced relativeto the acoustic wave device 400. The measurement results of FIGS. 6A and6B indicate that a buffer layer between layers of a multilayer IDTstructure can reduce stress in an acoustic wave device.

FIG. 7A-1 shows a simulated stress distribution in the acoustic wavedevice 400 that includes a molybdenum (Mo) IDT layer. FIG. 7A-2 shows asimulated stress distribution in the acoustic wave device 500 accordingto an embodiment that includes a molybdenum (Mo) IDT layer. Unlessotherwise noted, components of FIGS. 7A-1 and 7A-2 are the same orgeneral similar to the like components of FIGS. 4-6B. As shown in FIGS.7A-1 and 7A-2 , a lower stress is observed in the acoustic wave device500 as compared to the acoustic wave device 400.

The simulation result of FIG. 7A-1 indicates that a maximum stress inthe dielectric film 410 of the acoustic wave device 400 is about 260MPa. Meanwhile, the simulation result of FIG. 7A-1 indicates that amaximum stress in the dielectric film 510 of the acoustic wave device500 is about 168 MPa. Therefore, the simulation results of FIGS. 7A-1and 7A-2 indicate that the maximum stress can be reduced by adding thebuffer layer 520 (e.g., a Ti layer).

FIG. 7B-1 shows a simulated stress distribution in the acoustic wavedevice 400 that includes a tungsten (W) IDT layer. FIG. 7B-2 shows asimulated stress distribution in the acoustic wave device 500 accordingto an embodiment that includes a tungsten (W) IDT layer. Unlessotherwise noted, components of FIGS. 7B-1 and 7B-2 are the same orgeneral similar to the like components of FIGS. 4 to 6A-2 . As indicatedin FIGS. 7B-1 and 7B-2 , the acoustic wave device 500 which includes thebuffer layer 520 formed of Ti has improved reliability as compared tothe acoustic wave device 400 without the buffer layer 520.

The simulation result of FIG. 7B-1 indicates that a maximum stress inthe dielectric film 410 of the acoustic wave device 400 is about 276MPa. Meanwhile, the simulation result of FIG. 7A-1 indicates that amaximum stress in the dielectric film 510 of the acoustic wave device500 is about 188 MPa. Therefore, the simulation results of FIGS. 7B-1and 7B-2 indicate that the maximum stress can be reduced by adding thebuffer layer 520 (e.g., a Ti layer).

FIG. 7C-1 shows a simulated stress distribution in the acoustic wavedevice 400 that includes a platinum (Pt) IDT layer. FIG. 7C-2 shows asimulated stress distribution in the acoustic wave device 500 accordingto an embodiment that includes a platinum (Pt) IDT layer. Unlessotherwise noted, components of FIGS. 7C-1 and 7C-2 are the same orgeneral similar to the like components of FIGS. 4 to 6B-2 . As indicatedin in FIGS. 7C-1 and 7C-2 , the acoustic wave device 500 which includesthe buffer layer 520 formed of Ti has improved reliability with comparedto the acoustic wave device 400 without the buffer layer 520.

The simulation result of FIG. 7C-1 indicates that a maximum stress inthe dielectric film 410 of the acoustic wave device 400 is about 128MPa. Meanwhile, the simulation result of FIG. 7A-1 indicates that amaximum stress in the dielectric film 510 of the acoustic wave device500 is about 96 MPa. Therefore, the simulation results of FIGS. 7C-1 and7C-2 indicate that the maximum stress can be reduced by adding thebuffer layer 520 (e.g., a Ti layer).

FIG. 8A-1 is a graph showing simulated stress distribution along a sideedge of the IDT electrode 404 of FIG. 7A-1 that includes a molybdenum(Mo) layer. FIG. 8A-2 is a graph showing simulated stress distributionalong a side edge of the electrode 504 of FIG. 7A-2 that includes aplatinum (Mo) layer. The positions in the graphs indicate distances fromthe surfaces of the substrates 402, 502 to which the IDT electrode 404and the electrode 504 are positioned.

The simulation result of FIG. 8A-1 indicates that a maximum stress inthe lower layer of the acoustic wave device 400 is about 260 MPa. Theposition in which the maximum stress is observed is at about 80 nm whichcorresponds to the boundary between the lower layer 406 and the upperlayer 408.

Meanwhile, the simulation result of FIG. 8A-2 indicates that a maximumstress in the lower layer 506 (the Mo layer) of the acoustic wave device500 is about 168 MPa at about 80 nm. In addition, the overall stress isgenerally reduced in the acoustic wave device 500 as compared to theacoustic wave device 400. Therefore, the reliability of the acousticwave device 500 of FIG. 7A-2 is improved relative to the acoustic wavedevice 400 of FIG. 7A-1 .

FIG. 8B-1 is a graph showing simulated stress distribution along a sideedge of the IDT electrode 404 of FIG. 7B-1 that includes a tungsten (W)layer. FIG. 8B-2 is a graph showing simulated stress distribution alonga side edge of the electrode 504 of FIG. 7B-2 that includes a platinum(W) layer. The positions in the graphs indicate distances from thesurfaces of the substrates 402, 502 to which the IDT electrode 404 andthe electrode 504 are positioned.

The simulation result of FIG. 8B-1 indicates that a maximum stress inthe lower layer of the acoustic wave device 400 is about 276 MPa. Theposition in which the maximum stress is observed is at about 80 nm whichcorresponds to the boundary between the lower layer 406 and the upperlayer 408.

Meanwhile, the simulation result of FIG. 8B-2 indicates that a maximumstress in the lower layer 506 (e.g., the W layer) of the acoustic wavedevice 500 is about 188 MPa at about 80 nm. In addition, the overallstress is generally reduces in the acoustic wave device 500 as comparedto the acoustic wave device 400. Therefore, the reliability of theacoustic wave device 500 of FIG. 7B-2 is improved relative to theacoustic wave device 400 of FIG. 7B-1 .

FIG. 8C-1 is a graph showing simulated stress distribution along a sideedge of the IDT electrode 404 of FIG. 7C-1 that includes a platinum (Pt)layer. FIG. 8C-2 is a graph showing simulated stress distribution alonga side edge of the electrode 504 of FIG. 7C-2 that includes a platinum(Pt) layer. The positions in the graphs indicate distances from thesurfaces of the substrates 402, 502 to which the IDT electrode 404 andthe electrode 504 are positioned.

The simulation result of FIG. 8C-1 indicates that a maximum stress inthe lower layer of the acoustic wave device 400 is about 128 MPa. Theposition in which the maximum stress is observed is at about 80 nm whichcorresponds to the boundary between the lower layer 406 and the upperlayer 408. Meanwhile, the simulation result of FIG. 8B-2 indicates thata maximum stress in the lower layer 506 (the Pt layer) of the acousticwave device 500 is about 96 MPa at 80 nm. In addition, overall stress isgenerally reduces in the acoustic wave device 500 as compared to theacoustic wave device 400. Therefore, the reliability of the acousticwave device 500 of FIG. 7C-2 is improved relative to the acoustic wavedevice 400 of FIG. 7C-1 .

FIG. 9A is a graph showing the maximum stress along the electrode 504 inthe acoustic wave device 500 simulated with different thicknesses of thebuffer layer 520. FIG. 9A indicates that the maximum stress can bereduced as the thickness of the buffer layer is increases from ‘0’. Whenthe thickness of the buffer layer 520 is too thin (e.g., less than about5 nm, less than about 10 nm, or less than 20 nm), the buffer layer maynot sufficiently work as the transition layer between the lower layer506 and the upper layer 508. Therefore, it may be beneficial to form atleast certain thickness of the buffer layer 520. According to someembodiments, the thickness of the buffer layer 520 can be 20 nm orgreater.

On the other hand, at some point, the stress on the dielectric film 510is maintained at certain level regardless of the thickness of the bufferlayer. In other words, there may be little or no benefit, particularlyin terms of design and spacial aspect, to increase the thickness of thebuffer layer 520 over a certain level of the thickness. According tosome embodiment, the thickness of the buffer layer 520 can be less than1000 nm. For example, the buffer layer 520 can have a thickness in arange of 20 nm to 1000 nm, 20 nm to 200 nm, 20 nm to 100 nm, 30 nm to200 nm, or 50 nm to 100 nm. In some embodiments, the thickness of thebuffer layer 520 can be in a range of 5% to 30%, 10% to 30%, or 5% to20% of the total thickness of the electrode 504.

FIG. 9B is a schematic cross-sectional side view of an acoustic wavedevice 500′ according to an embodiment. The acoustic wave device 500′can be a temperature compensated surface acoustic wave (TC-SAW) device.The acoustic wave device 500′ can include a substrate 502 (e.g., apiezoelectric layer), an interdigital transducer (IDT) electrode 524,and a dielectric film 510 (e.g., a temperature compensation layer). TheIDT electrode 524 can include a first layer 526, a second layer 528 overthe first layer 526, a first buffer layer 530 between the first layer526 and the substrate 502, and a second buffer layer 532 between thefirst layer 526 and the second layer 528.

The first and second layers 526, 528 can be structurally andfunctionally the same as or generally similar to the lower layer 506 andthe upper layer 508, respectively. The first and second buffer layers530, 532 can be structurally and functionally the same as or generallysimilar to the buffer layer 520 disclosed herein. In some embodiments,the first layer 530 can release stress between the substrate 502 and thefirst layer 526, and the second buffer layer 532 can release stressbetween the first and second layers 526, 528. In some embodiments, theremay be more IDT layers

In some embodiments, the IDT electrode 524 can have a slanted or slopedsidewall. For example, the sidewall of the IDT electrode 524 can beslanted or sloped such that a width of an upper side of the first layer526 that faces the second layer 528 can be greater than a width of alower side of the second layer 528 that faces the first layer 526.

The principles and advantages disclosed herein can be implemented in anytemperature compensated surface acoustic wave (TC-SAW) devices. TheTC-SAW device can be implemented in a variety of electronic systems.

FIG. 10A is a schematic diagram of one embodiment of a packaged module800. FIG. 10B is a schematic diagram of a cross-section of the packagedmodule 800 of FIG. 10A taken along the lines 10B-10B.

The packaged module 800 includes an IC or die 801, surface mountcomponents 803, wirebonds 808, a package substrate 820, andencapsulation structure 840. The package substrate 820 includes pads 806formed from conductors disposed therein. Additionally, the die 801includes pads 804, and the wirebonds 808 have been used to electricallyconnect the pads 804 of the die 801 to the pads 806 of the packagesubstrate 820.

The die 801 includes a filter module, which can be implemented inaccordance with any of the embodiments herein.

The packaging substrate 820 can be configured to receive a plurality ofcomponents such as the die 801 and the surface mount components 803,which can include, for example, surface mount capacitors and/orinductors.

As shown in FIG. 10B, the packaged module 800 is shown to include aplurality of contact pads 832 disposed on the side of the packagedmodule 800 opposite the side used to mount the die 801. Configuring thepackaged module 800 in this manner can aid in connecting the packagedmodule 800 to a circuit board such as a phone board of a wirelessdevice. The example contact pads 832 can be configured to provide RFsignals, bias signals, power low voltage(s) and/or power high voltage(s)to the die 801 and/or the surface mount components 803. As shown in FIG.16B, the electrically connections between the contact pads 832 and thedie 801 can be facilitated by connections 833 through the packagesubstrate 820. The connections 833 can represent electrical paths formedthrough the package substrate 820, such as connections associated withvias and conductors of a multilayer laminated package substrate.

In some embodiments, the packaged module 800 can also include one ormore packaging structures to, for example, provide protection and/orfacilitate handling of the packaged module 800. Such a packagingstructure can include overmold or encapsulation structure 840 formedover the packaging substrate 820 and the components and die(s) disposedthereon.

It will be understood that although the packaged module 800 is describedin the context of electrical connections based on wirebonds, one or morefeatures of the present disclosure can also be implemented in otherpackaging configurations, including, for example, flip-chipconfigurations.

FIG. 11 is a schematic diagram of one embodiment of a phone board 900.The phone board 900 includes the packaged module 800 shown in FIGS.10A-10B attached thereto. Although not illustrated in FIG. 10 forclarity, the phone board 900 can include additional components andstructures. Some of the embodiments described above have providedexamples in connection with wireless devices or mobile phones. However,the principles and advantages of the embodiments can be used for anyother systems or apparatus that have needs for power amplifiers.

Such envelope trackers can be implemented in various electronic devices.Examples of the electronic devices can include, but are not limited to,consumer electronic products, parts of the consumer electronic products,electronic test equipment, etc. Examples of the electronic devices canalso include, but are not limited to, memory chips, memory modules,circuits of optical networks or other communication networks, and diskdriver circuits. The consumer electronic products can include, but arenot limited to, a mobile phone, a telephone, a television, a computermonitor, a computer, a hand-held computer, a personal digital assistant(PDA), a microwave, a refrigerator, an automobile, a stereo system, acassette recorder or player, a DVD player, a CD player, a VCR, an MP3player, a radio, a camcorder, a camera, a digital camera, a portablememory chip, a washer, a dryer, a washer/dryer, a copier, a facsimilemachine, a scanner, a multi-functional peripheral device, a wrist watch,a clock, etc. Further, the electronic devices can include unfinishedproducts.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of this disclosure is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, thisdisclosure are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of this disclosure provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of this disclosure have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A temperature compensated surface acoustic wavedevice comprising: a piezoelectric layer; an interdigital transducerelectrode over the piezoelectric layer, the interdigital transducerelectrode including a first layer, a second layer over the first layer,and a buffer layer between the first layer and the second layer, athermal conductivity of the second layer being greater than a thermalconductivity of the buffer layer, a thickness of the buffer layer beingin a range of 20 nm to 200 nm; and a temperature compensation layer overthe interdigital transducer electrode.
 2. The surface acoustic wavedevice of claim 1 wherein the piezoelectric layer is a lithium niobatelayer having a cut angle in a range of 116° to 134° and a thickness in arange of 100 μm and 350 μm.
 3. The surface acoustic wave device of claim1 wherein the thermal conductivity of the buffer layer is greater than athermal conductivity of the first layer.
 4. The surface acoustic wavedevice of claim 1 wherein the interdigital transducer electrode has atapered sidewall.
 5. The surface acoustic wave device of claim 4 whereina width of the first layer is greater than a width of the second layer.6. The surface acoustic wave device of claim 1 wherein a thickness ofthe buffer layer is in a range of 20 nm to 100 nm.
 7. The surfaceacoustic wave device of claim 1 wherein a thickness of the buffer layeris in a range of 5% to 30% of a thickness of the interdigital transducerelectrode.
 8. The surface acoustic wave device of claim 1 wherein athickness of the buffer layer is a titanium layer or a chromium layer.9. A temperature compensated surface acoustic wave device comprising: apiezoelectric layer; an interdigital transducer electrode over thepiezoelectric layer, the interdigital transducer electrode including afirst layer, a second layer over the first layer, and a titanium bufferlayer between the first layer and the second layer, a thickness of thetitanium buffer layer being in a range of 20 nm to 200 nm; and atemperature compensation layer over the interdigital transducerelectrode.
 10. The surface acoustic wave device of claim 9 wherein thepiezoelectric layer is a lithium niobate layer having a cut angle in arange of 116° to 134° and a thickness in a range of 100 μm and 350 μm.11. The surface acoustic wave device of claim 9 wherein the first layeris a molybdenum layer, a tungsten layer, or a platinum layer, and thesecond layer is an aluminum layer.
 12. The surface acoustic wave deviceof claim 9 wherein the interdigital transducer electrode has a taperedsidewall, and a width of the first layer is greater than a width of thesecond layer.
 13. The surface acoustic wave device of claim 9 wherein athickness of the titanium buffer layer is in a range of 20 nm to 100 nm.14. The surface acoustic wave device of claim 9 wherein a thickness ofthe titanium buffer layer is in a range of 5% to 30% of a thickness ofthe interdigital transducer electrode.
 15. A temperature compensatedsurface acoustic wave device comprising: a piezoelectric layer; aninterdigital transducer electrode over the piezoelectric layer, theinterdigital transducer electrode including a first layer, a secondlayer over the first layer, and a buffer layer between the first layerand the second layer, a thermal conductivity of the second layer beinggreater than a thermal conductivity of the buffer layer, a thickness ofthe buffer layer being in a range of 5% to 30% of a thickness of theinterdigital transducer electrode; and a temperature compensation layerover the interdigital transducer electrode.
 16. The surface acousticwave device of claim 15 wherein the piezoelectric layer is a lithiumniobate layer having a cut angle in a range of 116° to 134° and athickness in a range of 100 μm and 350 μm.
 17. The surface acoustic wavedevice of claim 15 wherein the first layer is a molybdenum layer, atungsten layer, or a platinum layer, and the second layer is an aluminumlayer.
 18. The surface acoustic wave device of claim 15 wherein theinterdigital transducer electrode has a tapered sidewall, and a width ofthe first layer is greater than a width of the second layer.
 19. Thesurface acoustic wave device of claim 15 wherein a thickness of thebuffer layer is in a range of 20 nm to 200 nm.
 20. The surface acousticwave device of claim 15 wherein a thickness of the buffer layer is atitanium layer or a chromium layer.